1. Field of the Invention
The field of the invention is data processing, or, more specifically, methods, apparatus, and products for link-level data communications.
2. Description of Related Art
The development of the EDVAC computer system of 1948 is often cited as the beginning of the computer era. Since that time, computer systems have evolved into extremely complicated devices. Today's computers are much more sophisticated than early systems such as the EDVAC. Computer systems typically include a combination of hardware and software components, application programs, operating systems, processors, buses, memory, input/output devices, and so on. As advances in semiconductor processing and computer architecture push the performance of the computer higher and higher, more sophisticated computer architectures have evolved to take advantage of the higher performance of the hardware, resulting in computer systems today that are much more powerful than just a few years ago.
One of the areas that has seen substantial improvement is data communications through packet switching. Today many systems provide processing of data communications packets that is transparent to the operations of the source computer, the sender, and the destination of the packets. That is, neither the source nor the ultimate destination of the packets is ever made aware that such transparent processing occurs. Such transparent processing may include for example security processing, load balancing functions among data communications equipment, statistical surveys, and so on. Such transparent processing can include processing by not just one, but several interim service applications, one providing security services, another performing statistical surveys, another performing load balancing, and so on.
When data packets are to be processed by several service applications the problem of routing the data stream from one service application to another naturally arises. For service applications that carry out packet analysis and therefore operate in ‘bump-in-the-wire promiscuous mode,’ that is, transparently and invisibly sitting between two or more networking devices listening to all packets exchanged between the devices, preserving the packet headers is required. Because such service applications commonly perform inspection on the packet headers and the payload, the entire packet—payload+headers—must be considered “payload” to this kind of service application. Each such bump-in-the-wire service application must return each packet it handles to the communications system with the original header addresses intact so as not to interfere with the overall transmission of the packet from its original source to its ultimate destination.
Prior art has attempted to solve this problem by encapsulating the entire packet—payload+headers—and wrapping it with a new header that specifies the routing of the packet to bump-in-the-wire applications. This new encapsulation header must be understood by all the various hardware, switches, NICs, and so on, and potentially even by the bump-in-the-wire service applications themselves. This requirement to process this additional layer of headers is a burden to hardware developers and application providers who must now design, develop, test, and support an additional configuration of their core product. In addition, some solutions require that application providers not only integrate new header processing, but also port their application to specific hardware and operating system platforms.
Another solution attempted in prior art was to modify packets in certain ways, such as changing the destination MAC address, for example. This option changes the packet and limits the ability to perform the types of analysis that rely on possession of the original addresses in the packet. Moreover, this solution requires hardware developers to provide additional modifications of routers, bridges, and switches that use it to track the original addresses and return them to the packets upon return from the bump-in-the-wire service applications.